Forrest W. Christian wrote:
The consumer (Dialup,DSL,Cable, Wireless broadband,etc) internet is
slowly moving to this, with one minor exception:
Marc Perkel wrote:
If port 25 were blocked from consumers and they were forced to talk to
servers on port 587, even without authentication, then a server could
distinguish consumers from other servers. I think this kind of
configuration could be used to help isolate virus infected computers
from spamming and spreading.
587 should *always* be authenticated. In this way, it prevents unknown
users within your address space from using your email server to spew
spam. All mail that originates from a server configured in this way (25
is only for other mail servers, and cannot relay, 587 is always
authenticated, and permits relaying), can then be tracked back to the
original user to help eliminate spam at the source.
Most ISP's which implement the 25 block will open if the customer is
running their own mail server.
You can get this same effect without caring about the port number. Just
require SMTP-AUTH for relaying. This is easily achieved, you just
remove any hosts you don't directly control from your relay domain(s).
That means your clients (no matter which port they're using) will have
to use SMTP-AUTH to relay out to the outside world. Hosts that don't
use SMTP-AUTH (no matter which port they connect to, and without regard
to whether they're a client or a remote relay) will have to be sending
to your local recipients.
